<!DOCTYPE html>
<html>
<head>
	<meta charset="utf-8">
	<meta http-equiv="X-UA-Compatible" content="IE=edge">
	<title></title>
	<link rel="stylesheet" href="">
</head>
<body>
<div id='root'>
	{{a}}
</div>
<script src="Observer-Watcher-Vue.js"></script>	
<script>
	var vm = new Vue({
		data : {
			a:1,
		}
	})
	console.log(vm.a);
	setTimeout(()=>{vm.a = 2},2000);
	vm.$watch('a',()=>console.log('哈哈,$watch检测成功'));
	console.log(vm.a);
	console.log(vm)
</script>
</body>
</html>